artists: convert other_names to array (#3987).

db/migrate/20181114202744_change_other_names_to_array_on_artists.rb

@@ -0,0 +1,23 @@
+class ChangeOtherNamesToArrayOnArtists < ActiveRecord::Migration[5.2]
+  def up
+    Artist.without_timeout do
+      remove_index :artists, name: "index_artists_on_other_names_trgm"
+      change_column :artists, :other_names, "text[]", using: "array_remove(regexp_split_to_array(other_names, '\\s+'), '')", default: "{}"
+      add_index :artists, :other_names, using: :gin
+
+      remove_column :artists, :other_names_index
+      execute "DROP TRIGGER trigger_artists_on_update ON artists"
+    end
+  end
+
+  def down
+    Artist.without_timeout do
+      remove_index :artists, :other_names
+      change_column :artists, :other_names, "text", using: "array_to_string(other_names, ' ')", default: nil
+      add_index :artists, :other_names, name: "index_artists_on_other_names_trgm", using: :gin, opclass: :gin_trgm_ops
+
+      add_column :artists, :other_names_index, :tsvector
+      execute "CREATE TRIGGER trigger_artists_on_update BEFORE INSERT OR UPDATE ON artists FOR EACH ROW EXECUTE PROCEDURE tsvector_update_trigger('other_names_index', 'public.danbooru', 'other_names')"
+    end
+  end
+end